How the individual sensory modalities relate to one another and how their functions are integrated during development has been the subject of increasing research attention. Studies that manipulate the amount, type, or timing of sensory experience over prenatal and early postnatal development are, however, difficult to undertake with human infants and a comparative approach utilizing animal embryos and infants offers a useful and important step in experimentally examining such issues. Recent evidence derived from precocial avian embryos and neonates has demonstrated that prenatal stimulation in one sensory modality can influence responsiveness to stimulation in other sensory modalities, showing the strong link between the modalities during early development. The bases for these effects remains unexplored. The primary goal of this proposed research is to identify the roles played by unimodal and multimodal sensory stimulation in the emergence and maintenance of early intersensory perception. Nine experiments utilizing precocial avian embryos and hatchlings are proposed that examine the roles of embryonic arousal and attention in early intersensory responsiveness, assess the role of intersensory redundancy in the perceptual learning of embryos and hatchlings, investigate the role of amodal temporal and spatial stimulus properties in the detection and processing of multimodal stimulation, and assess the features of social interaction that foster the emergence of intersensory functioning. The findings of the proposed research will provide basic behavioral data on the experiential processes that underlie perinatal intersensory perception, contribute to a better understanding of the complex relationship between prenatal and postnatal ontogeny, and provide an important source of comparative data for the research projects of Bahrick, Mundy, and Rochat concerned with intersensory development in the human infant.